Recently, sanitary napkins have been developed which contain components other than wood pulp fluff, a fluid pervious cover, and a fluid impermeable baffle. The inclusion of materials with heightened absorbent capabilities but reduced bulk such as superabsorbent materials and surfactant treated meltblown microfiber webs have allowed the production of thin sanitary napkins with adequate capacity. Furthermore, it has been recognized that sanitary napkins which contain wood pulp fluff or similar cellulosic absorbent material can benefit from the addition or substitution in part of a layer of material containing thermoplastic fibers. Conventional cellulosic absorbents, when wet, are extremely uncomfortable because cellulosic capillaries tend to collapse with the addition of fluid. To overcome this tendency, multilayer napkins have been constructed in which a layer overlying the wood pulp fluff layer incorporates thermoplastic fibers. These fibers are more hydrophobic than cellulosic fibers and capillaries formed by these fibers do not collapse when wet. Because of the inclusion of the fibers, however, there may be a reduced capacity when compared to the conventional cellulosic fibers and this is certainly the case when a layer containing both thermoplastic and wood pulp fibers are compared to absorbent material such as superabsorbents.
U.S. Pat. No. 4,100,324 discloses a process for making a cover material for a sanitary napkin which is a turbulently airlaid mixture of wood pulp fluff fibers and meltblown microfibers. The merging of separate streams of these fibers producing a turbulent air flow results in a web with ample integrity. The properties of this web may be manipulated by varying such things as its basis weight, the amount, diameter, and type of meltblown microfibers employed as well as the relationship of such a web to other components in a sanitary napkin. It is apparent that by manipulating these properties the absorbency, the tactual properties and the z direction transfer of the web can be manipulated over a substantial range.
NEW FREEDOM.RTM. Maxithins sanitary napkins have recently been marketed which employ a coformed web as an intermediate layer between nonwoven cover material and a surfactant treated meltblown microfiber layer.
The additional nonwoven layer is needed because of the difficulty in obtaining adhesive bonding through an overlapped layer of the coform material.
As disclosed in U.S. Pat. No. 3,672,371, issued to Robert J. Roeder, a pressure sensitive garment attachment adhesive can be employed which attaches a sanitary napkin to a garment and penetrates and seals the overlapped portion of the wrap of a sanitary napkin. Due to the comparatively thick dense nature of the coform layer compared to the nonwoven wrap, adhesive will not readily penetrate and also serve the garment attachment function.